Oscillating sander



May 26, 1953 K. c. ATKlN OSCILLATING SANDER 2 Sheets-Sheet 2 Filed Sept. 9, 1950 H ll l INVENTOR. f ezzrzeiii 6. QZ/flh Patented May 26, 1953 OSCILLATIN G SANDER Kenneth C. Atkin, Muskegon, Mich., assignor to Clarke, Sanding Machine Company, Muskegon, Mich., a corporation of Michigan Application September 9, 1950, Serial No. 183,920 3 Claims. (01. 51-470) This invention relates to surface treating machinery, and has specific reference to a portable oscillating sander having a motor driven, vibrating abrasive or polishing element adapted for free manipulation over a surface for smooth ing and fine finishing.

There has long been a recognized need for small, portable sanding and polishing machines, and many types of machines intended for this purpose have been proposed in the past. It has become fairly well known, however, that these prior art machines fall far short of full accomplishment of their intended purpose and include undesirable features which render them unsatisfactory in one respect or another. In most cases the machines have been so designed and constructed that the entire machine, including the handle portions or hand grips thereof, were subject to extreme vibration, rendering the machine hard to control and very tiring to the operator when in use. Also, in many cases, the machines have lacked durability and have been too short-lived to be commercially practicable. In addition, they have displayed a tendency to rattle, overheat, and to break down or shake themselves loose within a very short period of operation. The more elaborate machines designed to overcome these objectionable tendencies have been so inherently complex and expensive as to be unsalable in a highly competitive market.

It is, therefore, the general aim of the present invention to provide an improved oscillating sanding machine wherein the defects inherent in previously known machines of this general type are overcome, and to provide a simple, durable, low cost machine which is at the same time efficient, quiet, and easy to use.

A specific object of the invention is to provide an oscillating sander so designed and constructed as to impart energetic vibrating movement to the sanding pad, yet to do so in such a manner as to largely eliminate vibration of the other parts of the machine, particularly the motor housing and handles by which it is manipulated.

Another object of the invention is to provide a machine as indicated above including an auxiliary motor cooling fan disposed externally of the motor housing, so that the motor housing may be maintained at a temperature low enough that it is not uncomfortable to handle, notwithstanding that the machine is driven by a motor of conventional design and is operated under full load.

A further object of the invention is to provide an oscillating sander having a sanding ad to fan disposed between the motor and the sanding.

pad and serving the double function of eliminating vibration of the motor housing and handles, and supplementing the cooling effects of the internal cooling system of the motor. A still further object of the invention is the provision of an improved driving mechanism for an oscillating surface treating machine, wherein end thrust on the motor shaft crank and bearings is entirely eliminated. This is of marked advantage in several respects. For one thing, it minimizes wear on the bearings of the motor and permits the use of a motor having no end thrust bearings without sacrifice of long life of the machine. Moreover, it reduces wear and friction in the crank pin and bearing which convert the rotary motion of the motor into oscillating motion in the sanding paid. These effects result in eliminating undue friction throughout the moving parts, and thus result in a more efficient utilization of the power of the motor in driving the sanding pad. A still further advantage inherent in the construction employed to accomplish this object is that the need of maintaining extremely close tolerances is eliminated. In fact, considerable latitude in the fitting of parts may be permitted without disadvantageous effects.

Another important object of the invention is the provision of a machine wherein the sanding pad, motor housing and fan are so related with respect to each other that the air utilized to cool the motor is discharged away from the work and dissipated into the open air, rather than being allowed to blow across the surface being treated. This is of advantage in that it results in a machine capable of operation with much less dust than developed by other types. It also results in more efficient abrasive action, since any grit or sand dislodged from the sanding pad is not blown away, but remains on the surface being treated and continues to function as an abrasive agent thereon.

A further object of the invention is the provision of a portable motor driven sanding machine wherein the sanding pad is directly driven by a crank on the motor shaft and is mounted by improved yieldable mounts, which permit vibratory movement of the pad in any lateral direction without undue noise or rattle, yet afford adequate support to maintain the fixed spacing desired between the motor housing and the pad.

The foregoing objects are accomplished in the present teaching by a relatively simple mechanism consisting essentially of a motor with a small crank pin directly coupled to the center of a vibratory sanding pad, with a plurality of flexible rubber mounting studs supporting the pad from the motor, and a counterweighted fan positioned between the motor and the pad serving th double function of cooling the motor and compensating for the inertia of the sanding pad to reduce vibration of the motor and handles thereon.

A preferred embodiment of the present invention is illustrated in the drawings of the present specification, wherein:

Figure 1 is a plan view of a sanding machine according to this invention;

Figure 2 is a side elevational view thereof, shown partially in section along. the plane or! the line 2-2 of Figure 1;

Figure 3 is an enlarged detail plan sectional view taken substantially on the plane of the line 3-3 of Figure 2-;

Figure 4- is an enlarged detail sectional view taken substantially on the plane. of the. iine'4--4 of Figure 2 and. illustrating the flexible rubber mountings for the sanding pad; and- Figure 5 is av side elevational viewof the counterweighted fan employed; herein.

The. sanding; machine disclosed herein com. prises a, relatively flatsanding. pad mounted on a frame which consistsof; a motor housing lzl attached to a. flanged stamping l2 and provided with outwardly extending handles l3; and (.4. The motor H is verticallydisposed, withits armature shaft l5. projecting: downwardly through a bearing I6. Air inlets iii are formed in. the upper end of the motor housing, and. coacting air outlets. (not. shown). are located at the lower end of the housing: adjacent thev bearing 16..

Ordinarily, smallmotors of the type utilizedi ment the action of the internal motor fan by:

other cooling means, sothat the motor housing is maintained at a sufficiently lowtemperature that it may be handled by the operator without discomfort, even after long continueduse of the machine.

The sheet metalstamping I2 is secured to the lower end of the motor by a numberof'machine screws i9, and a resilient rubber gasket 2! is interposed between the stamping and the motor housing so as to-provide-afirm; vibrationless-joint between the parts, so that theseparts, with the handles l3 and 14, form a unitary frame for-themachine. The handle ['4 includes a switch 2-!- and serves as a connection fora line cord- 22' to which the motor leads 23 are connected.

The flanged stamping I 2' is of generally rec'- tangular shape and is perforated adjacent its four corners to receive the upper ends ofaplurality of flexible rubber mounting posts'24. Each of these plugs is of solid rubber, consisting of. a generally cylindrical lower section 25 connected to a grooved top section 26 by a reduced neck. The lower sections 25 are provided portion 21. with molded-in inserts 2'8 threaded. to receive machine screws 29, by which the lower ends of" themountings are secured to the flat sheetjmetal backing plate 31 of the sanding pad l0; shown, the sanding pad has' a resilient rubber facing 32 under the metal" backing plate 31.

The sandingpad I9 is positively driven from the motor shaft 15 by means of an offset crank 34 having a sleeve portion 35 fitted over the end of the motor shaft. The sleeve portion 35 of the crank also carries a counterweighted fan 36, the hub 3! of which is secured to the sleeve and motor shaft by means of set screws 38 and 39.

The-fan 36- i nclfudes a plurality of curved radial fins 4| extending upwardly from a circular disc or plate which is relatively thin on one side of the fan as indicated at 42 (Figure 5), but is of considerably greater thickness in the portions 43 on the other side, so that the fan is effective as a counterbalance. for the crank pin 34. The counterweighted fan thus compensates for the inertia effects of the sanding pad l0, and functions to confine. the. vibration of the mechanism to this pad and its associated parts, and to substantially' eliminate vibration of the frame, motor, and handles.

The lower end of the crank 34-" extends into a ball, bearing. M mounted in a cup 45 formed. as an integral part of the metal backing plat 3|- of, the sanding. pad; Thus, as the motor revolves, thev entire: sanding pad H] is vibrated. The rubber mounting posts 24 yield sufficientl-y to permit unrestricted lateral. movement of the pad in any direction, yet these: posts maintain the sanding pad. in properly spaced relationship with the motor and the frame stamping; 1-2. The metal backing plate 3-! of the sanding pad l0 includes upwardly extending flangesv 4% at its ends and side flanges 49 along: each. side. These flanges. add to the rigidity of the: pad and at the same time function as air deflectors, so: that the. air discharged outwardly from the fan 36' is directed". upwardly and away fromthe work; With this arrangement, the. blast. of airfrom the fan is dissipated in free air rather thanbeing: directed against the workingv surface, and; as aconsequence-, very: little dust is created by the action.

of. the. machine. Also, anygrit and which isdislodgedfrom: the sandpaper tends to remain.

on the working surface. and. continue its: abrasive function, rather. than being. blown; away;

It is contemplatedthat in. the: use of. the. ma.-

chine; a. sheet of sandpaper Willi besecured. across: the: lowermost. surface ofi the rubber facing 32* on.

the. sanding; pad lsfli. Means; are: accordingly provided to hold. the sandpaper sheet in position firmly, yet in a manner such that. itv may be easily'removed and replaced whenrequireda,

As illustrated, the:- sandpaper sheet-v 5 If extends across the bottomofi the rubber surface oil the sanding pad and has ends passed upwardly and doubled back. around: the end flanges: 41] of the sandingtpad.. The free. ends 5220f the sheet. are held under wire springs- 53: pivoted; on crosspins 54' and pressed: downwardly against: the

sandpaper" by double. coil springs 55. carried on.

the pins 54'. Each: coil' 55: hastwo endportions. 56 bearing: downwardly against the end portions of the springs. 53 and acenter portion 51: resting against the uppevsurface of the. metal plate 3| of the sanding pad. The spring 53/ has an. upwardly ofi set bail portion 58 intermediate its ends: to facilitate manual lifting of thespring inremoving and: replacing the sandpaper sheet.

Fromthe above it will be apparent that the present invention provides a vibrating sander which is mechanically simple and relatively inex pensiveto manufacture, yet is at the same time durable, quiet and efiicient. It is to be particularly noted that the sander here disclosedv accomplishes a positive mechanical drive from the motorto the-sanding'pad, yetincludes a counterweight so disposed as to compensate for the inertia of the pad and. its associated parts, so that the pad will be energetically vibrated by the motor, but the frame and handles of the device will be relatively free of vibration. This results in a machine that is easy to use, yet is highly efficient in operation.

It is also to be noted that the action of the internal fan ordinarily provided in conventional motors is supplemented by the counterweighted fan of this disclosure in such a manner that cool running of the motor is assured, and it should be further noted that this is accomplished by the same mechanism which compensates for the inertia of the sanding pad and eliminates motor vibration. This is a feature making for simple, rugged, low cost construction.

It is to be further pointed out that the machine is of such design and construction that its operation does not raise an appreciable amount of dust, primarily for the reason that the air used to cool the motor is directed away from the work so that it does not blow dust into the air. The machine is also of such design and construction that friction and unnecessary Wear due to end thrust on the motor shaft or crank pin is eliminated, yet the pad is so mounted as to move freely in any lateral direction. Moreover, the resilient character of the rubber mounting pads eliminates noisy metal parts and has an inherent capacity for silencing the mechanism so that there is no tendency toward chattering or rattling.

Having thus described my invention, what I claim as new and desire to secure by United States Letters Patent is:

1. In a sanding machine, the combination of a frame, a vibratory sanding pad, and laterally yieldable mounting means consisting of a, plurality of independent rubber posts interconnecting the sanding pad with the frame; said frame including a motor having a rotary driving shaft disposed perpendicularly to the sanding pad with a crank pin on said driving shaft in operative engagement with said sanding pad and an eccentric counterweight secured to the driving shaft adjacent the crank pin to compensate for the inertia of the sanding pad and reduce vibration of the motor housing; said counterweight including a centrifugal fan positioned adjacent one end of the motor and adapted to draw air therethrough, with upwardly directed flanges along the marginal edges of the sanding pad to direct the air discharged from the fan upwardly and outwardly away from the work.

2. In a sanding machine, the combination of a frame, a vibratory sanding pad, and laterally yieldable mounting means consisting of a plurality of independent rubber posts interconnecting the sanding pad with the frame; said frame including a motor having air inlet and outlet ports and an internal fan constructed and arranged to draw ambient air through said motor; with a crank pin on said driving shaft of said motor in operative engagement with said sanding pad; together with an eccentric counterweight secured to the driving shaft adjacent the crank pin to compensate for the inertia of the sanding pad and reduce vibration of the motor housing, said counterweight including a centrifugal fan positioned immediately adjacent the air outlet ports of the motor and adapted to augment the action of the internal fan to draw additional air therethrough, with upwardly directed flanges along the marginal edges of the sanding pad to direct the air discharged from the fan upwardly and outwardly away from the work.

3. In a sanding machine, the combination of a frame, a motor thereon, a vibratory sanding pad, and a plurality of separate flexible mounting members spaced apart from each other and interconnecting the sanding pad with the frame; said mounting members each consisting of a rubher post yieldable in at least two lateral directions to permit unrestricted lateral vibratory movement of said pad with respect to the frame; with a rotary driving shaft extending from the motor tothe pad and disposed perpendicularly to the sanding pad, and a crank pin on said driving shaft directly engaging an anti-friction bearing fixed to said sanding pad; together with an eccentric counterweight secured tov the motor shaft adjacent the crank pin to compensate for the inertia of the sanding pad and reduce vibration of the motor housing, said counterweight including a centrifugal fan adjacent one end of the motor housing to draw air therethrough and upwardly directed flanges around the periphery of said pad adapted to direct the. air from said fan upwardly and outwardly away from the work.

KENNETH C. ATKIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,177,824 Siberzohn Apr. 4, 1916 2,100,020 Andrews Nov. 23, 1937 2,143,970 Blood Jan. 17, 1939 2,270,309 Kehle Jan. 20, 1942 2,284,671 Meinzer June 2, 1942 2,292,567 Jordan Aug. 11, 1942 2,367,668 Champayne Jan. 23, 1945 2,415,993 Cottrell Feb. 18, 1947 2,545,942 Crosby et a1 Mar. 20, 1951 

